Modelling of pollutant dispersion with atmospheric instabilities in an industrial park

Abstract

Large Eddy Simulation (LES) combined with a dynamic Smagorinsky subgrid scale model was used to simulate the wind field and particulate pollutant dispersion considering the effects of plant canopies and weather conditions. The model of the plant canopy was adopted to present the effects of drag force and buoyancy force and validated by bench mark results from previous reference. Then, using the model, four study cases in the Nanjing Sample Industrial Park were simulated under different weather conditions to consider the momentum effect of plant canopy, energy effect of plant canopy and the effect of atmospheric instabilities, respectively. The numerical results were also compared with those of idealized street canyon models, and it was proven that the accurate landform model was more practical to be applied in the study. The wind field and pollutant distribution were analyzed in each case to investigate the influence of plant canopy. It was shown that the wind velocity was lower near the canopy regions, especially in unstable conditions due to the entrainment effect of the buoyancy force. Meanwhile, the streamline could be changed by the buoyancy force in an upward trend. The distribution of the turbulent kinetic energy indicated that the turbulent flow in the atmosphere was weakened through the plant canopy, especially in unstable conditions. Considering the effect of buoyancy force, the direction of pollutant dispersion in horizontal profiles was different to the neutral condition, which proved that plant canopy can protect the downstream regions in unstable atmospheric conditions.